Gregory Chanan created HBASE-7051:
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Summary: Read/Updates (increment,checkAndPut) should properly read
MVCC
Key: HBASE-7051
URL: https://issues.apache.org/jira/browse/HBASE-7051
Project: HBase
Issue Type: Bug
Affects Versions: 0.96.0
Reporter: Gregory Chanan
See, for example:
{code}
// TODO: Use MVCC to make this set of increments atomic to reads
{code}
Here's an example of what I can happen (would probably be good to write up a
test case for each read/update):
Concurrent update via increment and put.
The put grabs the row lock first and updates the memstore, but releases the row
lock before the MVCC is advanced. Then, the increment grabs the row lock and
reads right away, reading the old value and incrementing based on that.
There are a few options here:
1) Waiting for the MVCC to advance for read/updates: the downside is that you
have to wait for updates on other rows.
2) Have an MVCC per-row (table configuration): this avoids the unnecessary
contention of 1)
3) Transform the read/updates to write-only with rollup on read.. E.g. an
increment would just have the number of values to increment.
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